security: harden CI against supply-chain attacks (#20476)

- Pin all third-party actions to SHA
- Gate claude.yml triggers to internal authors with Harden-Runner egress
audit
- Ignore fork-PR lifecycle scripts
- Narrow cross-repo dispatch payloads
- Add 7d npm release-age gate
- Add CODEOWNERS on .github/** and .yarnrc.yml

---------

Co-authored-by: prastoin <paul@twenty.com>

.github/workflows/ci-merge-queue.yaml

@@ -41,11 +41,11 @@ jobs:
         ports:
           - 6379:6379
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
         with:
           fetch-depth: 10
 
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
           node-version: lts/*
 
@@ -53,7 +53,7 @@ jobs:
         uses: ./.github/actions/yarn-install
 
       - name: Restore Nx build cache
-        uses: actions/cache/restore@v4
+        uses: actions/cache/restore@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0 (restore)
         with:
           key: v4-e2e-build-${{ github.ref_name }}-${{ github.sha }}
           restore-keys: |
@@ -83,7 +83,7 @@ jobs:
 
       - name: Save Nx build cache
         if: always()
-        uses: actions/cache/save@v4
+        uses: actions/cache/save@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0 (save)
         with:
           key: v4-e2e-build-${{ github.ref_name }}-${{ github.sha }}
           path: |
@@ -119,7 +119,7 @@ jobs:
 
       - name: Upload Playwright results
         if: always()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
         with:
           name: playwright-results
           path: |